1. Field of the Invention
The present invention relates to a workpiece container assembly and to an apparatus for opening/closing the container of the assembly. More particularly, the present invention relates to a container assembly for accommodating semiconductor wafers in the course of their being processed, and to an apparatus for opening and closing a cover of the container assembly.
2. Description of the Related Art
Semiconductor devices are fabricated by subjecting a wafer to various manufacturing processes, such as photolithography, deposition, etching, and thin film-forming processes. These wafers are typically 8 inches in diameter. The wafers are accommodated in a container and from there are introduced into the manufacturing apparatus in which the above-mentioned processes are carried out. As the technology behind these processes has improved, wafers having a diameter of 12 inches are being used in addition to the 8-inch wafers.
An open wafer cassette is mainly used to accommodate the wafers when the wafers have a diameter of 8 inches. Recently, however, a closed-type of container assembly, for example, a front open unified pod (hereinafter, simply referred to as a “FOUP”) has been developed for use with the larger 12-inch wafers. The FOUP is better than an open wafer cassette in preventing the wafers from being contaminated when the wafers are transferred to and from the manufacturing apparatus.
The FOUP includes a container in which the wafers are accommodated, and a cover disposed over the front of the container. In addition, a separate opening/closing apparatus is used to remove the cover from the container. An example of such a FOUP is disclosed in U.S. Pat. No. 6,186,331 issued to Kinpara, et al.
Hereinafter, a conventional FOUP and an apparatus for opening/closing the FOUP will be described with reference to FIGS. 1 and 2.
The FOUP 10 includes a container 12 for accommodating wafers therein, and a cover 14 covering an open side of the container 12 so as to close the container 12. The container 12 also has opposite sidewalls which define therein a series of parallel slots 16. The wafers W are inserted into the slots 16, respectively. On the other hand, the cover 14 includes a main cover body, and a locking section 18. The container 12 has a frame 30 which cooperates with the locking section 18 so that the cover 14 may be attached to and detached from the container 12.
Referring to FIG. 2, the locking section 18 includes a plate 20 that is rotatably supported within the body of the cover 14. The rotatable plate 20 has a keyhole 22 in the center thereof. The keyhole 22 is exposed at the front of the cover 14 such that a key can be inserted into the keyhole 22 from outside of the cover 14. When a user rotates the key after inserting the key into the keyhole 22, the plate 20 is rotated.
The locking section 18 of the cover 14 also includes a pair of bars 24. First ends of the bars 24 are connected to the rotatable plate 20, and second ends of the bars 24 protrude from the body of the cover 14 through upper and lower surfaces of the cover 14, respectively. A respective inlet hole 26 extends through each of the upper and lower surfaces of the cover 14 to allow the bars 24 to protrude from the cover 14.
The frame 30 is integral with the container 12 and has insertion holes 32 (shown in FIG. 1) which are positioned across from inlet holes 26 of the cover 14 so as to receive the bars 24 of the cover 14 when the cover 14 is attached to the container 12. That is, the bars 24 of the locking section 18 are inserted into the insertion holes 32 formed in the frame 30 so that the cover 14 is coupled to the container 12, thereby closing the FOUP 10.
The FOUP 10 having the above structure requires a separate opening/closing apparatus for operating the cover 14 to open/close the container 12.
Generally, the opening/closing apparatus includes a loading section which supports the FOUP 10 and is operable to move the FOUP 10 horizontally, a plate that will face the cover of a FOUP 10 supported by the loading section, a key mounted on a side of the plate so as to be insertable into the keyhole 22 of the FOUP, and a drive mechanism for moving the plate vertically or horizontally. One example of such a FOUP opening/closing apparatus is disclosed in U.S. Pat. No. 6,053,688 (issued to Cheng).
Next, the operation of the FOUP opening/closing apparatus will be described.
First, a closed FOUP 10 accommodating a plurality of wafers to be processed is placed on the loading section. Then, the FOUP 10 is moved horizontally towards the plate until the plate and the cover 14 engage each other. At this time, the key mounted on the plate is inserted into the keyhole 22 in the front of the cover 14.
Subsequently, the key is rotated. As a result, the plate 20 is rotated and the bars 24 connected to the rotating plate 20 are moved vertically so that second ends of the bars 24 are withdrawn into the cover 14. Accordingly, the cover 14 can be separated from the container 12. In addition, since the key is inserted into the keyhole 22, the cover 14 is attached to the plate.
Then, the plate to which the cover 14 is attached is moved horizontally to detach the cover 14 from the container. The plate is then moved vertically so as to open the FOUP 10.
However, the keyhole 22 formed in the cover of the conventional FOUP 10 is very small and thus, the key of the opening/closing apparatus is also very small. Accordingly, the key cannot be precisely aligned with the keyhole 22 when the cover 14 of the FOUP 10 is to be separated from the container 12. Therefore, sometimes the FOUP 10 is not be opened.
In addition, the FOUP 10 is frequently opened/closed during the semiconductor manufacturing process and hence, the key is frequently inserted into the keyhole 22 and is rotated while in the keyhole 22. For this reason, the keyhole 22 becomes enlarged, and eventually a gap is formed between the key and the keyhole 22. If a large gap is formed between the key and the keyhole 22, the opening/closing apparatus may not be able to rotate the key within the keyhole 22. In this case, an opening/closing error of the FOUP 10 occurs. As a result, the processing time is increased and the productivity of the semiconductor manufacturing process is correspondingly decreased.